Difference Between Crossing Over and Linkage

Difference Between Crossing Over and Linkage: Crossing over and linkage are two different but related events that influence the distribution of genes in the same chromosome. These two processes are seen in the case of eukaryotic cells only. On the same chromosome, the distance between two genes is directly proportional to their chance of crossing over whereas on the same chromosome, the distance between two genes is inversely proportional to their degree of linkage.

Crossing Over

When genes from chromosomes are exchanged between non-sister chromatids during the meiosis of gamete formation in sexual reproduction, it is called crossing over. It is the process of swapping genetic material in the germline or shuffling the genes from a pair of alleles to ensure that the gamete receives a combination of genes from both parents. This process ensures the genetic variation in sexually reproducing organisms and follows the law of segregation. This phenomenon was described by Morgan in 1909.

Linkage

The capability of certain closely positioned genes or DNA sequences on a chromosome to be transferred together from parent to gamete during meiosis of sexual reproduction is called linkage or genetic linkage. These genes should be located on the same chromosome. This phenomenon is an exception to Mendel’s Law of Independent Assortment and was discovered by Bateson, Saunders, and Punnett in 1905 while studying pollen’s flower color and shape on pea plants.

Crossing Over vs. Linkage

	Crossing  Over	Linkage
Definition	Exchange of genes from a pair of alleles between non-sister chromatids during gamete formation.	Closely positioned genes tend to get transferred together during gamete formation.
Purpose	Ensures segregation of genes to form a new pair of alleles.	To ensure that certain closely located genes are inherited together.
Effect of distance	Distance between two genes is directly proportional to the possibility of crossing over.	Distance between two genes is inversely proportional to the degree of linkage.
Result	It results in variation.	It results in maintaining parental traits in the offspring.
Significance	Ensures separation of genes.	Ensures inheritance of genes in their parental form.
Effect of Age	Increases with age.	Decreases with age.

FAQs

Q1: What is the effect of linkage during gametogenesis on the offspring?

Answer:

Linkage will result in the inheritance of a paired parental character as it is from one of its parents.

Q2: Give one example of a linked character.

Answer:

One of the linked characteristics in humans is genes for hair and eye color like brown hair with brown eyes.

Q3: What is a non-homologous crossover?

Answer:

When non-identical sister chromatids are formed due to sequence mismatch results in unequal interactions, it is called non-homologous crossover.

Q4: What is the effect of crossing over during gametogenesis on the offspring?

Answer:

Crossing over will result in a variation of characters in offspring.

Q5: What is a linkage map?

Answer:

It is a table that shows the position of genes based on their recombination frequency which follows the pattern that the more recombination frequency two genes have, their position will be apart from each other and vice-versa.